1. Field of the Invention
Embodiments of the present invention relate to an electron emission device, an electron emission type backlight unit including the same, and a method of manufacturing the same. More particularly, embodiments of the present invention relate to an electron emission device having an electrode structure capable of preventing an inter-electrode short, an electron emission type backlight unit including the electron emission device, and a method of manufacturing the same.
2. Description of the Related Art
Generally, electron emission devices may be classified into devices using a hot cathode as an electron emission source and devices using a cold cathode as an electron emission source. Examples of electron emission devices using cold cathodes as electron emission sources may include a Field Emission Device (FED), a Surface Conduction Emitter (SCE), a Metal Insulator Metal (MIM) device, a Metal Insulator Semiconductor (MIS) device, a Ballistic electron Surface Emitting (BSE) device, and so forth.
FEDs may include a material having a low work function or a high beta function as an electron emission source between electrodes, so application of voltage to the electrodes may cause electron emission in a vacuum due to an electric field difference. SCEs may include a conductive thin film with micro-cracks as an electron emission source between electrodes, so application of voltage to the electrodes may cause electrode emission from the micro-cracks when a current flows on a surface of the conductive thin. MIM/MIS devices may have a metal-dielectric layer-metal/semiconductor structures, respectively, so application of voltage to two metals having the dielectric layer therebetween or to a metal and a semiconductor having the dielectric layer therebetween may cause electron emissions from a high electron potential to a metal having a low electron potential. BSE devices may have a structure of an insulating layer between a metal and an electron supply layer, i.e., a metal layer or a semiconductor layer on an ohmic electrode, so application of voltage to the metal layer and the electron supply layer may cause electron emission due to a smaller size of the semiconductor than a mean-free-path of electrons therein, i.e., electron travelling without scattering.
A conventional electron emission device may include electrodes on a substrate and electron emission layers coated on the electrodes. An anode and a phosphor layer may be positioned to face the electrodes. Application of voltage to the plurality of electrodes may form an electric field therebetween, so electrons may be emitted from the electron emission layers. Application of voltage to the anode may accelerate the emitted electrons toward the anode to excite the phosphor layer.
The conventional electron emission device may have several structural problems. Firstly, distances between the electrodes on the substrate may be hard to adjust. In particular, if a distance between the electrodes is too small, an electrical short may be caused. If a distance between the electrodes is too large, electron emission may not be efficient. Further, it may be difficult to maintain a uniform distance between the electron emission layers on the electrodes.
Secondly, the electric field between the anode and electrodes may be stronger than the electric field between the electrodes on the substrate, so a diode emission may be caused, i.e., false emission of electrons to collide with unintended regions of the phosphor layer. The diode emission may cause unwanted light emission, i.e., incorrect pixel illumination. Accordingly, image quality may be reduced and power and light emitting efficiency of the electron emission device may be decreased. Attempts have been made to prevent diode emission by limiting voltage level applied to the anode, but a reduced voltage on the anode may reduce current density, so image brightness may be decreased. Attempts have been made to increase current density by increasing an amount of emitted electrons from the electron emission layers, but increased electron emission may reduce lifetime of the electron emission layers, so overall life time of the electron emission device may be decreased.